The host-feeding activity of Haemaphysalis longicornis nymphs (Acari : Ixodidae) in autumn observed under experimental conditions

The feeding activity of Haemaphysalis longicornis nymphs that were reared at 24℃ under a 16L-8D photoperiod from egg to engorged larva and then placed outdoors was observed under laboratory conditions (24℃, 16L-8D). The rate of engorgement of the nymphs fed on rabbits was high in October (about one month after molting) but decreased from November (about two months after molting). The rate of engorgement of the nymphs that were reared in the laboratory (24℃, 16L-8D) from egg to unfed nymph was high from October through December. These results suggest that behavioural diapause, which is induced by the short days of autumn, occurs in H. longicornis nymphs that have been placed outdoors. However, the rate of engorgement of the nymphs was more than 20% even in December. Thus, the proportion of the nymphs which enter diapause in autumn appears to be low.